Differing effects of substrate and non-substrate transport inhibitors on glutamate uptake reversal.
Differing effects of substrate and non-substrate transport inhibitors on glutamate uptake reversal.
复制标题
底物和非底物转运抑制剂对谷氨酸摄取逆转的不同影响。
DOI：
10.1046/j.1471-4159.2001.00668.x
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发表时间：
2001
影响因子：
4.7
通讯作者：
Swanson,RA
中科院分区：
文献类型：
--
作者：
Anderson,CM;Bridges,RJ;Chamberlin,AR;Shimamoto,K;Yasuda-Kamatani,Y;Swanson,RA
Na+依赖性兴奋性氨基酸转运蛋白（EAATs）通常具有从脑细胞外空间移除细胞外谷氨酸的功能，但EAATs也可以通过逆转摄取来增加细胞外谷氨酸。抑制剂对EAATs的影响可能是复杂的，这取决于细胞类型、条件是否有利于谷氨酸摄取或摄取逆转以及抑制剂本身是否是转运体的底物。本研究评估了EAAT抑制剂在星形胶质细胞和神经元培养中抑制谷氨酸摄取、作为转运底物和阻断摄取逆转的能力。l - tho - β -羟基天冬氨酸（l - TBHA）、l - tho - β -苄氧天冬氨酸（dl - TBOA）、ltrans -吡咯烷- 2,4 -二羧酸（ltrans - 2,4 - PDC）(+/ -) -顺- 4 -甲基-反- 2,4 -二羧酸（顺- 4 -甲基-反- 2,4 - PDC）和lantiendo - 3,4 -甲基吡咯烷- 2,4 -二羧酸（lantiendo - 3,4 - MPDC）抑制星形胶质细胞对l - [14C]谷氨酸的摄取，平衡结合常数范围为17 μ m(dl - TBOA和l - TBHA) - 43 μ m（顺- 4 -甲基-反- 2,4 - PDC）。在星形胶质细胞和神经元中评估抑制剂的可转运性。虽然- TBHA、ltrans - 2,4 - PDC、顺式- 4 -甲基- trans - 2,4 - PDC和lantiendo - 3,4 - MPDC在神经元和星形胶质细胞中显示出显著的转运蛋白底物活性，但dl - TBOA仅在星形胶质细胞中显示出底物活性。dl - TBOA的这种作用是浓度依赖性的，导致谷氨酸摄取逆转的复杂效应。当浓度低到足以产生最小的dl - TBOA摄取速度（≤10µm）时，dl - TBOA阻断了ATP耗尽星形胶质细胞的摄取逆转；这种阻断在大量驱动TBOA摄取的浓度（bbb10µm）下被否定。这些发现表明，EAAT抑制剂的净效应可以随细胞类型和暴露条件而变化。
Na+‐dependent excitatory amino acid transporters (EAATs) normally function to remove extracellular glutamate from brain extracellular space, but EAATs can also increase extracellular glutamate by reversal of uptake. Effects of inhibitors on EAATs can be complex, depending on cell type, whether conditions favor glutamate uptake or uptake reversal and whether the inhibitor itself is a substrate for the transporters. The present study assessed EAAT inhibitors for their ability to inhibit glutamate uptake, act as transporter substrates and block uptake reversal in astrocyte and neuron cultures.lthreo‐β‐hydroxyaspartate (l‐TBHA),dlthreo‐β‐benzyloxyaspartate (dl‐TBOA),ltrans‐pyrrolidine‐2,4‐dicarboxylic acid (ltrans‐2,4‐PDC) (+/–)‐cis‐4‐methy‐trans‐pyrrolidine‐2,4‐dicarboxylic acid (cis‐4‐methy‐trans‐2,4‐PDC) andlantiendo‐3,4‐methanopyrrolidine‐2,4‐dicarboxylic acid (lantiendo‐3,4‐MPDC) inhibitedl‐[14C]glutamate uptake in astrocytes with equilibrium binding constants ranging from 17 µm(dl‐TBOA andl‐TBHA) – 43 µm(cis‐4‐methy‐trans‐2,4‐PDC). Transportability of inhibitors was assessed in astrocytes and neurons. Whilel‐TBHA,ltrans‐2,4‐PDC,cis‐4‐methy‐trans‐2,4‐PDC andlantiendo‐3,4‐MPDC displayed significant transporter substrate activities in neurons and astrocytes,dl‐TBOA was a substrate only in astrocytes. This effect ofdl‐TBOA was concentration‐dependent, leading to complex effects on glutamate uptake reversal. At concentrations low enough to produce minimaldl‐TBOA uptake velocity (≤ 10 µm),dl‐TBOA blocked uptake reversal in ATP‐depleted astrocytes; this blockade was negated at concentrations that drove substantialdl‐TBOA uptake (> 10 µm). These findings indicate that the net effects of EAAT inhibitors can vary with cell type and exposure conditions.